Plastic seal

ABSTRACT

An all plastic seal in which the socket receiving the locking head of a strap connected to the seal body is provided with a housing open at both ends. The locking head is inserted into one end of the housing into locking engagement with resilient locking fingers. The tip of the locking head is tapered in a single plane which intersects the longitudinal centerline of the opening in the housing forming the socket. A stop shoulder is provided in a recessed part of the housing for engaging a corresponding stop member on the locking head to prevent inward movement of the locking head beyond the distance necessary to engage the locking fingers. The housing may also be provided with inwardly projecting flute-like projections for minimizing the freedom of movement of the locking head in its locked condition in a direction transverse to the longitudinal centerline of the housing and socket structure. Weakened portion may be provided immediately adjacent the tapered end surface of the locking head, immediately adjacent the shoulder on the locking head engaging with the locking fingers, and in the strap or tie member immediately adjacent the stop member. Each of these weakened places serves as an intentional breaking section for indicating unauthorized unlocking of the seal. A weakened portion in the form of a transverse bore adjacent the tapered surface of the locking head serves to cause expansion of the locking head in response to excess axial forces on said tapered surface. The end of the socket housing which accepts the locking head is conically shaped on the outside and thin walled at the extreme end of the housing to preclude excessive backing forces being applied with no visible signs of tampering when the head is axially forced.

United States Patent [1 1 [111 3,881,759 Fuehrer May 6, 1975 PLASTIC SEAL ing head is inserted into one end of the housing into [75] Inventor: Charles Fuehrer, Scarsdale, NY. P sngagemem wnh reslhem fi The up of the lockmg head is tapered 1n a slngle plane Assigneei Sloffel Seals cfll'lmrfllioll, New which intersects the longitudinal centerline of the York, opening in the housing forming the socket. A stop [22] Filed: Jan. 2 1973 shoulder provided in a recessed part of the housing for engaging a corresponding stop member on the PP 320,175 locking head to prevent inward movement of the lock- Related US. Application Data ing head beyond the distance necessary to engage the 63 locking fingers. The housing may also be provided 1 f;% ;3" 5 gg with inwardly projecting flute-like projections for minimizing the freedom of movement of the locking head 'ts locked condition in a direction transverse to the 52 us. c1. 292/321 51 Int. Cl. E05c 10/18; 865d 33/34 l f '::ga, ii'::;g ii gf' gs [58] Field of Search 292/317, 318, 319, 320, a P y P 292/32] 322 24]6 PB 30 5 P dlately ad acent the tapered end surface of the locking head, immediately adjacent the shoulder on the locking head engaging with the locking fingers, and in the [56] Reerences Clted strap or tie member immediately adjacent the stop UNITED STATES PATENTS member. Each of these weakened places serves as an 2,969,570 1/ Pari tal 292/322 intentional breaking section for indicating unautho- 33671701 2/1963 wenk,

292/32l rized unlocking of the sea]. A weakened portion in the all 8 fonn of a transverse bore adjacent the tapered surface o erg 3,590.442 7 1971 Geisinger.....1..........1.1....... 24/17 PB of the lockmg head Serves to cause expans'on of the Primary Examiner-Richard E. Moore Attorney, Agent, or FirmCraig & Antonelli [57] ABSTRACT An all plastic seal in which the socket receiving the locking head of a strap connected to the seal body is provided with a housing open at both ends. The locklocking head in response to excess axial forces on said tapered surface. The end of the socket housing which accepts the locking head is conically shaped on the outside and thin walled at the extreme end of the housing to preclude excessive backing forces being applied with no visible signs of tampering when the head is axially forced.

53 Claims, 6 Drawing Figures PATENTEDHAY scrs 2, 881 ,759

m/ FIGI H63 PLASTIC SEAL BACKGROUND AND SUMMARY OF THE INVENTION The present application is a continuation-in-part application of my copending application Ser. No. 89,542, filed Nov. 16, 1970, now US. Pat. No. 3,712,655, dated Jan. 23, I973. The subject matter of said copending application is incorporated herein by reference to the extent necessary for a complete understanding of the present invention.

The above-mentioned application related to an improved plastic seal which was relatively tamper proof and which could be manufactured in a single molding operation. One of the important features of the seal of the above-mentioned application related to the configuration of the housing bore surrounding the locking socket as open at both ends and with a ratio of length to diameter such as to substantially impede access to the locking prongs when the seal is in the closed condition. The construction of the housing bore as open at both ends facilitated the single step molding operation, since no additional steps were needed to close off the ends of the housing and socket bore. The construction of the length to diameter ratio so as to be sufficiently large made it rather difficult to obtain access to the locking head and/or locking prongs to wiggle the locking head free from the locking prongs without being detected. The above-mentioned application also disclosed an arrangement of longitudinally extending flutes arranged in the housing bore to abuttingly engage the sides of the locking head when in the locked position so as to substantially preclude transverse movement of the locking head in the event access to the locking head was obtained by a pencil, ball point pen or the like.

My invention disclosed and claimed in the abovementioned application exhibited a substantial improvement over prior art arrangements with respect to simplicity of manufacture combined with tamper proofness.

The invention of the above-mentioned application was particularly advantageous in substantially precluding undetectable transverse movement of either the locking head or the locking fingers. A further possibility of tampering with such a seal involves the application of very large axial forces on the locking head with respect to the socket housing to physically force the locking head past the locking fingers in a direction substantially opposite the locking direction. For example, if a sufficiently firm backing could be provided at the socket housing and a sufficiently large axial force could be applied on the locking head, a seal could, in some instances, be forced open in spite of provisions preventing transverse movements of the locking head and locking fingers.

The present invention is concerned with improving the tamper proofness of a seal of the general type disclosed in the above-mentioned application, while still maintaining the simple single molding step manufacturing possibilities. The present invention is particularly directed to improving tamper proofness with respect to unlocking by application of axial forces in the direction of the longitudinal centerline of the socket and locking head. The improved tamper proofing means of the present invention involve several constructional features of the socket and of the locking head, which features operate alone, in conjunction with one another, and in conjunction with features of the abovementioned application, to substantially improve the tamper proofness of a seal having a bore extending completely through the socket housing.

A first important tamper proofing feature of the present invention is the arrangement of the tip of the locking head means with a single inclined plane surface portion which is non-symmetrically disposed with respect to the longitudinal centerline of the locking head and socket structure. By this arrangement of the tip of the locking head, it becomes substantially more difficult to apply a large force in the direction of the head centerline. Also, by extending the tapered surface portion completely across the end of the locking head a tampering tool will slide to or be engageable with any force only at the junction of the surface portion and the socket walls, which junction is spaced from the centerline such that forces will cause tilting" or "cocking" of the locking head to prevent axial withdrawal. Also, even if one engaged a pointed pin into the inclined surface, such pin would necessarily be so sharp" that it would be extremely difficult to locate and engage the exact centerline on the inclined surface to avoid a tilting of the locking head. On the other hand, the arrangements having a symmetrical locking head surface (especially flat transverse surfaces) with respect to the longitudinal centerline, one could possibly exert a very large axial force on the locking head in the centerline direction.

Further, it would be practically impossible to engage a pin at the exact centerline and to further apply forces only in the centerline direction, and therefore tilting of the locking head would be caused by transverse force components. This tilting would cause a jamming of the locking head against the socket walls and the locking fingers, which jamming would prevent an unlocking of the seal.

A further tamper proofing constructional feature of the present invention includes the arrangement of a weakened portion immediately adjacent the locking head. This weakened portion forms a place of intentional radial expansion of the head in the event of excessive forces exerted on the head such that the force operates to lock the expanded head more firmly in the locking fingers. According to a preferred embodiment of the present invention, the stop shoulder on the socket or housing is provided at the end of a recess having a cross sectional shape the same as the cross sectional shape of the stop member on the locking head such that, in the locked position, both longitudinal and radial movement of the locking head is precluded. The dimensioning of the length of the recess is such that the walls of the housing bore prevent direct access to the stop member on the locking head.

A further important tamper proofing feature of the present invention relates to the configuration of the locking socket housing so as to make it more difficult to apply firm back-up" forces at the housing to accommodate the large axial forces on the locking head to unlock the seal. In a preferred embodiment of the present invention, the end of the housing which accepts the locking head (which end would have to be backed-up" to permit large axial forces on the locking head in the unlocking direction) is constructed with a very thin walled extreme end portion which conically tapers to thicker housing walls in the axial direction of the housing. The conical outer surface is difficult to symmetrically back-up with simple block members and the like. The thin walled extreme end portion will show outward signs of tampering if attempts are made to apply backing forces thereto. Further, sufficient housing strength is obtained by the thicker walled parts spaced from the extreme end portion.

The above-discussed tamper proofing features of the present invention operate separately and in conjunction with one another to substantially improve the tamper proofness of a seal, and especially of a seal of the type having a housing bore open at both ends to facilitate single step molding. These abovediscussed features also cooperate with the specific tamper proofing features disclosed in the above-mentioned co-pending application to provide for a substantially tamper proof seal of the simpliest construction. In this connection, it is noted that the tamper proofing features related to the relative length and diameter of the housing bore and relating to the longitudinal flutes in the housing bore described in the above-identified application may advantageously be used in conjunction with the novel tamper proofing features of the present invention as pointed out in the above discussion.

The above-discussed and further features, objects, and advantages of the present invention will become more obvious from the following description when taken in conjunction with the accompanying drawings, which shows, for purposes of illustration only, a single embodiment in accordance with the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an elevational view of an all-plastic padlock seal in accordance with the present invention, illustrating the socket and housing thereof in axial longitudinal cross-section;

FIG. 2 is a bottom plan view of the seal of FIG. 1;

FIG. 3 is a partial cross-sectional view taken along line Ill-Ill of FIG. 1;

FIG. 4 is a view similar to FIG. 2, and showing certain details thereof on an enlarged scale;

FIG. 4a is a cross-sectional view taken along line lV-IV of FIG. 3; and

FIG. 5 is a partial cross-sectional view taken along line V-V of FIG. 4.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now to the drawings, wherein like reference numerals are used throughout the various views to designate like parts, and more particularly to FIGS. 1 to 3, a flexible tie-member 1 has one end connected to a housing 2 and the other free end connected to a locking head 3. The housing 2 is provided with a longitudinally extending bore 4 extending completely through the housing 2 and arranged symmetrically with respect to longitudinal centerline 5. Near the end of the housing 2 attached to the tie-member 1, a locking socket arrangement is provided for lockingly accepting the locking head 3 during locking of the seal.

The locking head 3 includes a cylindrical stop member portion 6 which exhibits stop surfaces 6' engageable with correspondingly shaped stop shoulder surfaces 7 of the locking socket. Immediately outwardly of the stop member 6, a cylindrical section 8 is provided on the locking head 3. A conical part 9 is arranged between the cylindrical part 8 and the locking shoulders 10. A second cylindrical portion 11 extends from shoulders 10 outwardly to the planar end surface 12 of the locking head. This planar surface 12 extends at an angle of approximately 45 or less (steeper incline than 45) with respect to the longitudinal centerline 5 when in the seal locking position. A weakened section 13 in the form of a transverse hole is provided in the cylindrical part 11 between tapered surface 12 and locking shoulder 10.

The housing 2 is formed of a cylindrical sleeve 14 open at the bottom end and provided at the top with a flaring section 15. The thickness of the housing walls at the extreme end of the flaring section 15 are such that any substantial backing forces" BF (FIG. 1) will show visible tampering signs. Since flaring section tapers to cylindrical sleeve 14, no transverse backing shoulder is provided. The upper portion 16 of the longitudinal bore 4 has a diametric dimension slightly larger than the diametric dimension of stop shoulder 6. Intermediate portion 17 of bore 4 is delimited by the edges of locking fingers 18 and has a diametric dimension slightly larger than the maximum diametric dimension of the cylindrical part 11 of the locking head, but smaller than the diametric dimension of the stop 6 such that the locking head 3 can be inserted into the bore 4 with the head portion 11, 12, tapering section 9 and cylindrial section 8 until the stop 6 abuts against the stop shoulder 7 of the housing. The prong-like locking fingers 18, each of which defines on the inside thereof a part of a frustro-conical surface complementary to the surface of section 9, extend inwardly and downwardly within the housing 2, thus forming a circumferentially interrupted tapering section 19 of frustroconical shape. The length of the frustro-conical section 19 formed by the locking fingers is substantially equal to or very slightly larger than the length of the taperings section 9 and the length of the cylindrical section 17 is substantially equal to or very slightly larger than the length of the cylindrical section 8 so that the head portion 11, 12 snaps into its locked position with the locking shoulder surface 10 engaging against the end surfaces 18' of the prong-like fingers 18 when the stop member surfaces 6' are in abutting engagement with stop shoulder 7.

Since the bore 4 in seal housing 2 extends completely through the housing, there is a possibility that one could gain access to the tip of the locking head to attempt to unlock the seal without showing any signs of tampering. In the above-mentioned copending application, the ratio of the length L to the diameter D (See FIG. 3) was made relatively large, for example greater than 5:2, to preclude access to the prongs 18, particularly if the diametric dimension D is relatively small, for example, of the order of a quarter inch or less. The above-identified application also suggested the provision of longitudinally extending inwardly projecting flutes 21 arranged at least immediately adjacent the inserted locking head portion to limit transverse movement of the locking head. The above-mentioned application also suggested that a tapering part, corresponding to part 9, could lead to a weakened portion causing intentional failure in the event of excessive force on the tie member and locking head.

The present invention includes further tamper proofing structural features and above and beyond those suggested in the above-mentioned application. First, the tapering end surface section 12 of the locking head precludes the application of a large force in the direction of the longitudinal centerline to unlock the head. That is, a pin or other member inserted through the lower end of the housing bore 4 would merely slip off the steeply inclined surface 12 making it very difficult to engage the locking head at its centerline to apply axial unlocking forces. Forces (EF in FIG. 2) at the junction of housing and tapered section would tend to tilt (dash lines) the locking head to further prevent unlocking. Also, even if one were able to engage a pin or the like into the inclined surface 12 at the centerline (CF in FIG. 2), it would be very difficult to force the locking head in only the axial direction since such a pin would practically always also impart some transverse force components to cause tilting and jamming of the locking head.

The transverse aperture 13 arranged immediately adjacent the tapering surface 12 provides for an intentional expansion of the locking head (see dash lines FIG. 2) in the event of excessive tampering forces (EF or CF) on the tapering surface 12. Consequently, even if one were able to engage the surface 12, the expansion of the locking head would prevent forcing of the locking head in the axial direction past the locking fingers. Also, failure of the head at 13 would provide visible evidence of tampering upon a cursory inspection of the seal.

By arranging the cross-section of stop shoulder 6 to correspond with cross-section 16 of the upper part of bore 4, both radial and axial movement of the locking head is precluded by engagement of stop member 6 with shoulder 7 and sidewalls 16. Further, by arranging the longitudinal dimension x of sidewall portion 16 as no less than the longitudinal dimension y of stop member 6, access to the stop member 6 from outside of the housing is substantially limited, thereby further precluding radial and axial movement of the locking head with respect to the housing.

The connection between the tie-member l and the housing 2 is conveniently made immediately below the level of the tapering section and in line with the shoulder 7 so as to minimize the complexity of the mold required for manufacture. An intentional failure aperture 22 may also be provided in the tie-member immediately adjacent the stop shoulder 6 so as to cause an intentional failure at that point in the event excessive forces are applied to the tie-member in attempts to pull the locking head out of the housing by way of the tiemember. In addition, the weakened section formed by aperture 22 facilitates intentional breaking of the tiemember when one wishes to unlock the seal.

It will be readily recognized from the above that the improved seal according to the present invention provides a substantially completely tamperproof structure which can be manufactured by single molding step. Any known suitable synthetic resinous material may be used for the plastic seal of the present invention and any suitable known molding techniques may be used for the purpose of molding the same.

While I have shown and described but a single embodiment in accordance with the present invention, it is understood that the same is not limited thereto, but is susceptible of numerous changes and modifications as known to those skilled in the art. For example, the various tamper proofing features, such as the tapered end section 12, the weakened section expansion at 13, and the thin walled and conically flared housing end 15 could be provided each alone, or in any combination with one another or with the features of the copendin g application to optimize the tamper proofness of the seal. Further, the weakened section 13 could be formed by other than cylindrical apertures. Also, the crosssection of the various parts of the locking head could be of polygonal construction, rather than cylindrical, with corresponding polygonal shaped recesses and openings in the housing 2 as shown in the copending application. Thus, it is obvious that the present invention is not limited to the details described and shown herein, and 1 therefore do not wish to be limited to the same, but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

I claim:

1. A sea] comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, the extreme free end of said head portion being positioned inside said bore at a spacing from said second bore end with said head means in a seal locking position, the extreme free end of said head portion which faces said second bore end when said head means is in aseal locking position including portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portion from said second bore end with respect to said centerline.

2. A seal according to claim 1, wherein said housing means has a substantially longitudinally extending cylindrical outer configuration, and wherein said tie member is constructed as a flat member having a maximum dimension corresponding to the diameter of the housing means, said housing being provided with a stop shoulder in said socket means for limiting the extent of insertion of said locking head means into said socket means, said tie member being attached to said housing means in the plane of the stop shoulder.

3. A seal according to claim 1, wherein all points of the surface of said extreme free end of said head portion lie in a single plane which intersects said centerline through said head portion at an angle of less than 4. A seal according to claim 3, wherein said single plane intersects said centerline through said head portion at an angle of less than 45.

5. A seal according to claim 3, wherein said head portion includes a first cylindrically shaped part extending between said single plane and said shoulder.

6. A seal according to claim 5, further including a weakening bore extending transversely through said first cylindrically shaped part, said weakening bore serving as an intentional radial expansion section for said head portion in the event of excessive tampering forces on said extreme free end of said head portion.

'7. A seal according to claim 3, wherein said bore is a longitudinally extending bore, and wherein said at least one locking elements includes a plurality of prong-like locking elements symmetrically arranged with respect to the centerline of said bore, the centerline of said bore coinciding with the centerline through said head portion when said head portion is inserted into said socket means.

8. A seal according to claim 7, wherein said bore is of cylindrical stepped cross-section along the length thereof from said first bore end to said locking elements.

9. A seal comprising: housing means, locking socket means arranged in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means to lock the seal, the socket means including inwardly projecting pronglike locking elements and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller crosssection, said head portion being dimensioned to elastically expand the prong-like locking elements during insertion thereof so that the locking shoulder snaps in behind the end surfaces of the prong-like locking elements when the head portion is inserted into said socket means, said housing having a longitudinally extending bore means open at both ends, one end portion of said bore means enclosing said socket means with said socket means extending substantially parallel to said bore means, said locking head means and locking socket means including tamper proofing means for preventing undetectable unlocking of said seal, wherein said tamper proofing means includes wea kening means adjacent the end of said head portion, said weakening means being configured such that said head portion expands transversely in response to force components in the unlocking direction along a longitudinal centerline of said locking head and socket means.

10. A seal comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with walls surrounding said bore adjacent said first bore end which walls exhibit a longitudinal cross-section tapering from a point at said first bore end to a greater thickness in the direction of the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end.

11. A seal according to claim 10, wherein the walls of said housing means at said first bore end are substantially thinner than the walls of said housing means adjacent said locking head when in the locked condition.

12. A seal according to claim 11, wherein a longitudinal cross-section of said walls taper from a point at said first bore end to a uniform thickness adjacent said locking head when in the locked condition.

13. A seal according to claim 12, wherein the extreme free end of said head portion which faces said second bore end with said head means in a seal locking position includes portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portions from said second bore end with respect to said centerline.

14. A seal according to claim 10, wherein the housing means is constructed such that when in a seal locking postion, the ratio of the distance between the innermost end of the extreme free end of said head portion and the second bore end and the smallest cross-section dimension of said second bore end is such as to substantially preclude access to the at least one locking element from said second bore end.

15. A seal according to claim 10, wherein said bore is a longitudinally extending bore, and wherein said at least one locking elements includes a plurality of prong-like locking elements symmetrically arranged with respect to the centerline of said bore, the centerline of said bore coinciding with the centerline through said head portion when said head portion is inserted into said socket means.

16. A seal according to claim 7, wherein the housing means is constructed such that when in a seal locking postion, the ratio of the distance between the innermost end of the extreme free end of said head portion and the second bore end and the smallest cross-section dimension of said second bore end is such as to substantially preclude access to the locking elements from said second bore end.

17. A seal according to claim 1, wherein the housing means is provided in said bore means with inwardly projecting means at least in the area behind the locking surface portion of the at least one locking element for substantially minimizing the freedom of movement of the head portion in the bore means, when in the locked position thereof, in a direction transverse to said longitudinal centerline.

18. A seal comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end, and wherein the housing means is provided in said bore means with inwardly projecting means at least in the area behind the locking surface portion of the at least one locking element for substantially minimizing the freedom of movement of the head portion in the bore means, when in the locked position thereof, in a direction transverse to said longitudinal centerline.

19. A seal comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectabale application of backing forces at said housing means adjacent said first bore end, and wherein said housing means has a substantially longitudinally extending cylindrical outer configuration, and wherein said tie member is constructed as a flat member having a maximum dimension corresponding to the diameter of the housing means, said housing being provided with a stop shoulder in said socket means for limiting the extent of insertion of said locking head means into said socket means, said tie member being attached to said housing means in the plane of the stop shoulder.

20. A seal comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein weakening means are provided adjacent the extreme free end of said head portion, said weakening means being configured such that said head portion expands transversely in response to force components in the unlocking direction along a longitudinal centerline of said locking head and socket means.

21. A seal according to claim 20, wherein said weakening means is a transverse bore through said head portion, and wherein that part of said head portion adjacent said transverse bore expands transversely.

22, A sea] according to claim 21, wherein the extreme free end of said head portion which faces said second bore end with said head means in a seal locking position includes portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portions from said second bore end with respect to said centerline.

23. A seal according to claim 21, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end.

24. A seal according to claim 21, wherein said bore is a longitudinally extending bore, and wherein said at least one locking elements includes a plurality of prong-like locking elements symmetrically arranged with respect to the centerline of said bore, the centerline of said bore coinciding with the centerline through said head portion when said head portion is inserted into said socket means.

25. A seal according to claim 20, wherein the housing means is constructed such that when in a seal locking postion, the ratio of the distance between the innermost end of the extreme free end of said head portion and the second bore end and the smallest cross-section dimension of said second bore end is such as to substantially preclude access to the locking elements from said second bore end.

26. A seal according to claim 20, wherein the housing means is provided in said bore means with inwardly projecting means at least in the area behind the locking surface portion of the at least one locking element for substantially minimizing the freedom of movement of the head portion in the bore means, when in the locked position thereof, in a direction transverse to said longitudinal centerline.

27. A seal according to claim 20, wherein said housing means has a substantially longitudinally extending cylindrical outer configuration, and wherein said tie member is constructed as a flat member having a maximum dimension corresponding to the diameter of the housing means, said housing being provided with a stop shoulder in said socket means for limiting the extent of insertion of said locking head means into said socket means, said tie member being attached to said housing means in the plane of the stop shoulder.

28. A seal according to claim 20, wherein the extreme free end of said head portion which faces said second bore end with said head means in a seal locking position includes portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portions from said second bore end with respect to said centerline.

29. A seal according to claim 28, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end.

30. A seal according to claim 22, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end.

31. A seal according to claim 30, wherein the housing means is provided in said bore means with inwardly projecting means at least in the area behind the locking surface portion of the at least one locking element for substantially minimizing the freedom of movement of the head portion in the bore means, when in the locked position thereof, in a direction transverse to said longitudinal centerline.

32. A seal according to claim 30, wherein said housing means has a substantially longitudinally extending cylindrical outer configuration, and wherein said tie member is constructed as a flat member having a maximum dimension corresponding to the diameter of the housing means, said housing being provided with a stop shoulder in said socket means for limiting the extent of insertion of said locking head means into said socket means, said tie member being attached to said housing means in the plane of the stop shoulder.

33. A seal according to claim 20, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end.

34. A seal according to claim 24, wherein said bore is of cylindrical stepped cross-section along the length thereof from said first bore end to said locking elements.

35. A seal according to claim 30, wherein the housing means is constructed such that when in a seal locking postion, the ratio of the distance between the innermost end of the extreme free end of said head portion and the second bore end and the smallest crosssection dimension of said second bore end is such as to substantially preclude access to the locking elements from said second bore end.

36. A seal comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end, wherein the extreme free end of said head portion which faces said second bore end with said head means in a seal locking position includes portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a nonsymmetrical spacing of points of the surface of said extreme free end of said head portions from said second bore end with respect to said centerline.

37. A seal according to claim 36, wherein all points of the surface of said extreme free end of said head portion lie in a single plane which intersects said centerline through said head portion at an angle of less than 38. A seal according to claim 37, wherein said single plane intersects said centerline through said head portion at an angle of less than 45.

39. A seal comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end, wherein said bore is a longitudinally extending bore, and wherein said at least one locking element includes a plurality of prong-like locking elements symmetrically arranged with respect to the centerline of said bore, the centerline of said bore coinciding with the centerline through said head portion when said head portion is inserted into said socket means, and wherein said bore is of cylindrical stepped cross-section along the length thereof from said first bore end to said locking elements.

40. A seal comprising: housing means, a bore extending in said housing means with first and second bore ends, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, the extreme free end of said head portion being positioned inside said bore at a spacing from said second bore end with said head means in a seal locking position, the extreme free end of said head portion which faces said second bore end when said head means is in a seal locking position including portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portion from said second bore end with respect to said centerline.

41. A seal according to claim 40, wherein all points of the surface of said extreme free end of said head portion lie in a single plane which intersects said centerline through said head portion at an angle of less than 90.

42. A seal comprising: housing means, a bore extending in said housing means with first and second bore ends, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein weakening means are provided adjacent the extreme free end of said head portion, said weakening means being configured such that said head portion expands transversely in response to force components in the unlocking direction along a longitudinal centerline of said locking head and socket means.

43. A seal according to claim 42, wherein the ex treme free end of said head portion which faces said second bore end with said head means in a seal locking position includes portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portions from said second bore end with respect to said centerline.

44. A seal comprising: housing means, a bore extending in said housing means with first and second bore ends, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with walls surronding said bore adjacent said first bore end which walls exhibit a longitudinal cross-section tapering from a point at said first bore end to a greater thickness in the direction of the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end.

45. A seal according to claim 44, wherein the extreme free end of said head portion which faces said second bore end with said head means in a seal locking position includes portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portions from said second bore end with respect to said centerline.

46. A seal according to claim 45, wherein weakening means are provided adjacent the extreme free end of said head portion, said weakening means being configured such that said head portion expands transversely in response to force components in the unlocking direction along a longitudinal centerline of said locking head and socket means.

47. A seal according to claim 44, wherein weakening means are provided adjacent the extreme free end of said head portion, said weakening means being configured such that said head portion expands transversely in response to force components in the unlocking direction along a longitudinal centerline of said locking head and socket means.

48. A seal comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end, said thinner walls being tapered with the thinnest portion thereof at said first bore end, said locking head including a stop member for limiting the extent of insertion of said locking head in said socket means, said stop member having a cross-section corresponding to the cross-section of said first bore end such that said stop member substantially fills the cross-section of said first bore end when said seal is in a locked condition.

49. A seal according to claim 48, wherein the tie member is attached directly to an end portion of the stop member, wherein said stop member has a crosssectional size substantially greater than the crosssectional size of the tie member, and wherein the end portion of said stop member attached to the tie member is located in said socket means spaced inwardly of said first bore end when said seal is in a locked condition.

50. A seal according to claim 48, wherein a longitudinally cross-section of said walls taper from a point at said end to a uniform thickness adjacent said locking head when in the locked condition.

51. A seal comprising: housing means, a bore extending inside of said housing means with first and second bore ends, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end, said thinner walls being tapered with the thinnest portion thereof at said first bore end, said locking head including a stop member for limiting the extent of insertion of said locking head in said socket means, said stop member having a cross-section corresponding to the cross-section of said first bore end such that said stop member substantially fills the cross-section of said first bore end when said seal is in a locked condition.

52. A seal according to claim 51, wherein the tie member is attached directly to an end portion of the stop member, wherein said stop member has a crosssectional size substantially greater than the crosssectional size of the tie member, and wherein the end portion of said stop member attached to the tie member is located in said socket means spaced inwardly of said first bore end when said seal is in a locked condition.

53. A seal according to claim 51, wherein a longitudinally cross-section of said walls taper from a point at said end to a uniform thickness adjacent said locking head when in the locked condition.

* i t i III 

1. A seal comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, the extreme free end of said head portion being positioned inside said bore at a spacing from said second bore end with said head means in a seal locking position, the extreme free end of said head portion which faces said second bore end when said head means is in a seal locking position including portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portion from said second bore end with respect to said centerline.
 2. A seal according to claim 1, wherein said housing means has a substantially longitudinally extending cylindrical outer configuration, and wherein said tie member is constructed as a flat member having a maximum dimension corresponding to the diameter of the housing means, said housing being provided with a stop shoulder in said socket means for limiting the extent of insertion of said locking head means into said socket means, said tie member being attached to said housing means in the plane of the stop shoulder.
 3. A seal according to claim 1, wherein all points of the surface of said extreme free end of said head portion lie in a single plane which intersects said centerline through said head portion at an angle of less than 90*.
 4. A seal according to claim 3, wherein said single plane intersects said centerline through said head portion at an angle of less than 45*.
 5. A seal according to claim 3, wherein said head portion includes a first cylindrically shaped part extending between said single plane and said shoulder.
 6. A seal according to claim 5, further including a weakening bore extending transversely through said first cylindrically shaped part, said weakening bore serving as an intentional radial expansion section for said head portion in the event of excessive tampering forces on said extreme free end of said head portion.
 7. A seal according to claim 3, wherein said bore is a longitudinally extending bore, and wherein said at least one locking elements includes a plurality of prong-like locking elements symmetrically arranged with respect to the centerline of said bore, the centerline of said bore coinciding with the centerline through said head portion when said head portion is inserted into said socket means.
 8. A seal according to claim 7, wherein said bore is of cylindrical stepped cross-section along the length thereof from said first bore end to said locking elements.
 9. A seal comprising: housing means, locking socket means arranged in said housing means, a tie member having a free end and an end operatively connected to saId housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means to lock the seal, the socket means including inwardly projecting pronglike locking elements and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically expand the prong-like locking elements during insertion thereof so that the locking shoulder snaps in behind the end surfaces of the prong-like locking elements when the head portion is inserted into said socket means, said housing having a longitudinally extending bore means open at both ends, one end portion of said bore means enclosing said socket means with said socket means extending substantially parallel to said bore means, said locking head means and locking socket means including tamper proofing means for preventing undetectable unlocking of said seal, wherein said tamper proofing means includes weakening means adjacent the end of said head portion, said weakening means being configured such that said head portion expands transversely in response to force components in the unlocking direction along a longitudinal centerline of said locking head and socket means.
 10. A seal comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with walls surrounding said bore adjacent said first bore end which walls exhibit a longitudinal cross-section tapering from a point at said first bore end to a greater thickness in the direction of the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end.
 11. A seal according to claim 10, wherein the walls of said housing means at said first bore end are substantially thinner than the walls of said housing means adjacent said locking head when in the locked condition.
 12. A seal according to claim 11, wherein a longitudinal cross-section of said walls taper from a point at said first bore end to a uniform thickness adjacent said locking head when in the locked condition.
 13. A seal according to claim 12, wherein the extreme free end of said head portion which faces said second bore end with said head means in a seal locking position includes portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portions from said second bore end with respect to said centerline.
 14. A seal according to claim 10, wherein the housing means is constructed such that when in a seal locking postion, the ratio of the distance between the innermost end of the extreme free end of said head portion and the second bore end and the smallest cross-section dimension of said second bore end is such as to substantially preclude access to the at least one locking element from said second bore end.
 15. A Seal according to claim 10, wherein said bore is a longitudinally extending bore, and wherein said at least one locking elements includes a plurality of prong-like locking elements symmetrically arranged with respect to the centerline of said bore, the centerline of said bore coinciding with the centerline through said head portion when said head portion is inserted into said socket means.
 16. A seal according to claim 7, wherein the housing means is constructed such that when in a seal locking postion, the ratio of the distance between the innermost end of the extreme free end of said head portion and the second bore end and the smallest cross-section dimension of said second bore end is such as to substantially preclude access to the locking elements from said second bore end.
 17. A seal according to claim 1, wherein the housing means is provided in said bore means with inwardly projecting means at least in the area behind the locking surface portion of the at least one locking element for substantially minimizing the freedom of movement of the head portion in the bore means, when in the locked position thereof, in a direction transverse to said longitudinal centerline.
 18. A seal comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end, and wherein the housing means is provided in said bore means with inwardly projecting means at least in the area behind the locking surface portion of the at least one locking element for substantially minimizing the freedom of movement of the head portion in the bore means, when in the locked position thereof, in a direction transverse to said longitudinal centerline.
 19. A seal comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectabale application of backing forces at said hOusing means adjacent said first bore end, and wherein said housing means has a substantially longitudinally extending cylindrical outer configuration, and wherein said tie member is constructed as a flat member having a maximum dimension corresponding to the diameter of the housing means, said housing being provided with a stop shoulder in said socket means for limiting the extent of insertion of said locking head means into said socket means, said tie member being attached to said housing means in the plane of the stop shoulder.
 20. A seal comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein weakening means are provided adjacent the extreme free end of said head portion, said weakening means being configured such that said head portion expands transversely in response to force components in the unlocking direction along a longitudinal centerline of said locking head and socket means.
 21. A seal according to claim 20, wherein said weakening means is a transverse bore through said head portion, and wherein that part of said head portion adjacent said transverse bore expands transversely.
 22. A seal according to claim 21, wherein the extreme free end of said head portion which faces said second bore end with said head means in a seal locking position includes portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portions from said second bore end with respect to said centerline.
 23. A seal according to claim 21, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end.
 24. A seal according to claim 21, wherein said bore is a longitudinally extending bore, and wherein said at least one locking elements includes a plurality of prong-like locking elements symmetrically arranged with respect to the centerline of said bore, the centerline of said bore coinciding with the centerline through said head portion when said head portion is inserted into said socket means.
 25. A seal according to claim 20, wherein the housing means is constructed such that when in a seal locking postion, the ratio of the distance between the innermost end of the extreme free end of said head portion and the second bore end and the smallest cross-section dimension of said second bore end is such as to substantially preclude access to the locking elements from said second bore end.
 26. A seal according to claim 20, wherein the housing means is provided in said bore means with inwardly projecting means at least in the area behind the locking surface portion of the at least one locking element for substantially minimizing the freedom of movement of the head portion in the bore means, when in the locked position thereof, in a direction transverse to said longitudinal centerline.
 27. A seal according to claim 20, wherein said housing means has a substantially longitudinally extending cylindrical outer configuration, and wherein said tie member is constructed as a flat member having a maximum dimension corresponding to the diameter of the housing means, said housing being provided with a stop shoulder in said socket means for limiting the extent of insertion of said locking head means into said socket means, said tie member being attached to said housing means in the plane of the stop shoulder.
 28. A seal according to claim 20, wherein the extreme free end of said head portion which faces said second bore end with said head means in a seal locking position includes portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portions from said second bore end with respect to said centerline.
 29. A seal according to claim 28, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end.
 30. A seal according to claim 22, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end.
 31. A seal according to claim 30, wherein the housing means is provided in said bore means with inwardly projecting means at least in the area behind the locking surface portion of the at least one locking element for substantially minimizing the freedom of movement of the head portion in the bore means, when in the locked position thereof, in a direction transverse to said longitudinal centerline.
 32. A seal according to claim 30, wherein said housing means has a substantially longitudinally extending cylindrical outer configuration, and wherein said tie member is constructed as a flat member having a maximum dimension corresponding to the diameter of the housing means, said housing being provided with a stop shoulder in said socket means for limiting the extent of insertion of said locking head means into said socket means, said tie member being attached to said housing means in the plane of the stop shoulder.
 33. A seal according to claim 20, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end.
 34. A seal according to claim 24, wherein said bore is of cylindrical stepped cross-section along the length thereof from said first bore end to said locking elements.
 35. A seal according to claim 30, wherein the housing means is constructed such that when in a seal locking postion, the ratio of the distance between the innermost end of the extreme free end of said head portion and the second bore end and the smallest cross-section dimension of said second bore end is such as to substantially preclude access to the locking elements from said second bore end.
 36. A seal comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder fOrmed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end, wherein the extreme free end of said head portion which faces said second bore end with said head means in a seal locking position includes portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portions from said second bore end with respect to said centerline.
 37. A seal according to claim 36, wherein all points of the surface of said extreme free end of said head portion lie in a single plane which intersects said centerline through said head portion at an angle of less than 90*.
 38. A seal according to claim 37, wherein said single plane intersects said centerline through said head portion at an angle of less than 45*.
 39. A seal comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end, wherein said bore is a longitudinally extending bore, and wherein said at least one locking element includes a plurality of prong-like locking elements symmetrically arranged with respect to the centerline of said bore, the centerline of said bore coinciding with the centerline through said head portion when said head portion is inserted into said socket means, and wherein said bore is of cylindrical stepped cross-section along the length thereof from said first bore end to said locking elements.
 40. A seal comprising: housing means, a bore extending in said housing means with first and second bore ends, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, the extreme free end of said head portion being positioned inside said bore at a spacing from said second bore end with said head means in a seal locking position, the extreme free end of said head portion which faces said second bore end when said head means is in a seal locking position including portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portion from said second bore end with respect to said centerline.
 41. A seal according to claim 40, wherein all points of the surface of said extreme free end of said head portion lie in a single plane which intersects said centerline through said head portion at an angle of less than 90*.
 42. A seal comprising: housing means, a bore extending in said housing means with first and second bore ends, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein weakening means are provided adjacent the extreme free end of said head portion, said weakening means being configured such that said head portion expands transversely in response to force components in the unlocking direction along a longitudinal centerline of said locking head and socket means.
 43. A seal according to claim 42, wherein the extreme free end of said head portion which faces said second bore end with said head means in a seal locking position includes portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portions from said second bore end with respect to said centerline.
 44. A seal comprising: housing means, a bore extending in said housing means with first and second bore ends, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with walls surronding said bore adjacent said first bore end which walls exhibit a longitudinal cross-section tapering from a point at said first bore end to a greater thickness in the direction of the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end.
 45. A seal accordiNg to claim 44, wherein the extreme free end of said head portion which faces said second bore end with said head means in a seal locking position includes portions which are angularly inclined with respect to a centerline through said head portion, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portions from said second bore end with respect to said centerline.
 46. A seal according to claim 45, wherein weakening means are provided adjacent the extreme free end of said head portion, said weakening means being configured such that said head portion expands transversely in response to force components in the unlocking direction along a longitudinal centerline of said locking head and socket means.
 47. A seal according to claim 44, wherein weakening means are provided adjacent the extreme free end of said head portion, said weakening means being configured such that said head portion expands transversely in response to force components in the unlocking direction along a longitudinal centerline of said locking head and socket means.
 48. A seal comprising: housing means, a bore extending completely through said housing means with first and second bore ends opening to the outside of said housing means, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being dimensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end, said thinner walls being tapered with the thinnest portion thereof at said first bore end, said locking head including a stop member for limiting the extent of insertion of said locking head in said socket means, said stop member having a cross-section corresponding to the cross-section of said first bore end such that said stop member substantially fills the cross-section of said first bore end when said seal is in a locked condition.
 49. A seal according to claim 48, wherein the tie member is attached directly to an end portion of the stop member, wherein said stop member has a cross-sectional size substantially greater than the cross-sectional size of the tie member, and wherein the end portion of said stop member attached to the tie member is located in said socket means spaced inwardly of said first bore end when said seal is in a locked condition.
 50. A seal according to claim 48, wherein a longitudinally cross-section of said walls taper from a point at said end to a uniform thickness adjacent said locking head when in the locked condition.
 51. A seal comprising: housing means, a bore extending inside of said housing means with first and second bore ends, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one inwardly projecting locking element and the head means including a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section, said head portion being diMensioned to elastically deflect the at least one locking element during insertion thereof so that the locking shoulder snaps in behind locking surface portions of the at least one locking element when the head portion is inserted into said socket means, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end, said thinner walls being tapered with the thinnest portion thereof at said first bore end, said locking head including a stop member for limiting the extent of insertion of said locking head in said socket means, said stop member having a cross-section corresponding to the cross-section of said first bore end such that said stop member substantially fills the cross-section of said first bore end when said seal is in a locked condition.
 52. A seal according to claim 51, wherein the tie member is attached directly to an end portion of the stop member, wherein said stop member has a cross-sectional size substantially greater than the cross-sectional size of the tie member, and wherein the end portion of said stop member attached to the tie member is located in said socket means spaced inwardly of said first bore end when said seal is in a locked condition.
 53. A seal according to claim 51, wherein a longitudinally cross-section of said walls taper from a point at said end to a uniform thickness adjacent said locking head when in the locked condition. 